1. Field of the Invention
The present invention relates to a photographic light-sensitive material and, more particularly, to a silver halide photograhic light-sensitive material.
2. Description of the Prior Art
Photographic light-sensitive materials generally comprise, for example, a silver halide photographic light-sensitive emulsion layer, an emulsion-protecting layer, a filter layer, an interlayer, an antihalation layer, a backing layer, a film base-undercoating layer, a baryta layer, a film support, and so forth.
These layers, except for the film support, usually contain a hydrophilic colloid, such as gelatin, as a carrier.
These light-sensitive materials containing a hydrophilic colloid (hereinafter the hydrophilic colloid is described by referring to "gelatin," which is a typical example thereof) are processed with various aqueous solutions differing in pH and/or temperature. However, the gelatin layer has a poor water resistance, and hence it has a tendency to swell so much in the aqueous solution that its mechanical strength is reduced, and, in an extreme case, it will be dissolved into the processing solution. This is a fatal defect as a layer constituting a photographic light-sensitive material.
It is well known to use compound for forming cross-linkages, called "hardeners," so as to improve the physical properties of gelatin.
Many compounds have been proposed as hardeners, such as, for example, aldehydes, active halogens, aziridines, epoxides, alkanesulfonic acid esters, active vinyl compounds, dehydrating condensers (e.g., dicyclohexylcarbodiimide, etc.), and the like.
However, these compounds are not fully suitable as hardeners for photographic light-sensitive materials.
For example, aldehydes cause fogging of light-sensitive nuclei due to their reducing properties. Aziridine compounds cause serious problems in their production or application due to their detrimental actions on the human body. Other compounds also impose various restrictions due to poor stability, difficulty in preparation, etc. Thus, there are not necessarily many practically valuable hardeners.
It is well known that active halogen compounds, such as methanesulfonic acid esters, active vinyl group-containing compounds, active carboxylic acid esters, and the like, are comparatively advantageous. For example, dichlorotriazine, described in U.S. Pat. No. 3,325,287, methanesulfonic acid esters described in U.S. Pat. No. 3,834,902, vinylsulfonyl group-containing compounds described in U.S. Pat. No. 3,490,911 and German Pat. application (OLS) No. 2,749,260, active esters described in U.S. Pat. No. 3,542,558, and the like are fairly good hardeners.
However, the hardeners described here are only one of many additives used in photographic light-sensitive materials, which typically include complicated combinations of numerous components.
That is, photographic light-sensitive materials are constituted by combinations of many additives such as silver halide emulsions, chemical sensitizers, optical sensitizers, antifogging agents, surfactants, color formers, etc., and thus even slight environmental changes can often lead to serious deterioration of important properties.
Hardeners have heretofore been used as necessary ingredients for photographic light-sensitive materials, but even the few good hardeners as described above cause a reduction in the pH with the progress of cross-linking reaction which is the essential characteristic of such hardeners. In fact, measurement of pH of the film reveals that all of the foregoing hardeners reduce pH.
Hardeners in the photographic light-sensitive materials which react with an amino group of gelatin in conventional pH ranges may, though quite rarely, react with a carboxy group of gelatin to increase pH in the extremely low pH range (e.g., pH of 2 to 3).
This reduction in pH exerts serious influences on the properties of photographic light-sensitive materials. The most serious of these are reduction in sensitivity, which is of critical importance in photographic light-sensitive materials, and regression of latent image become more by the reduction in pH. It is not a fundamental solution to these problems to raise the initial pH in order to avoid the reduction in sensitivity and regression of latent image caused by the reduction in pH with the lapse of time, because raising the pH initially causes an increase in fogging and a deterioration of color image preservability.
In addition, the reduction in the pH with the progress of the cross-linking reaction delays the hardening reaction itself, thus causing so-called "post hardening", which is a change in film properties due to hardening over a long period of time, and causes a reduction in attained hardness, apparently due to self-catalytic action of deterioration of the hardener.